The invention is directed to a programmed digital secondary clock. In particular, the invention is directed to a programmed digital microcomputer which functions either as a master clock, a sub-master clock, or a slave clock. Identical units can be remotely located and connected in daisy chain to provide a continuously updated real time count at remote locations such as in an airport, hospital, school, bank, hotel or government or industrial facility. Real time and corrected time are displayed numerically on a digital liquid crystal display. Each unit in the daisy chain is capable of operating in any of the foregoing modes. In any of the foregoing modes, the unit can be operated as an elapsed timer or as an interval timer. When operated as a slave clock in a chain of clocks, the clock can detect malfunction of a prior unit and automatically assume the function of a master clock to ensure continued operation of the following clocks in the chain.
Heretofore, electronic secondary clocks were not capable of selective operation as either master, sub-master or slave clocks. Moreover, conventional secondary clocks were not able to display corrected time without inordinate delays. In addition, the secondary clocks could not be connected in daisy chain to continuously provide real time counts without danger of failure of the entire chain upon malfunction of a single unit.
An advantage of the invention is that the programmed secondary clock can be selectively operated either as a master, sub-master or slave clock.
Another advantage of the invention is that corrected time information can be instantly displayed.
A further advantage of the invention is that identical units can be connected in daisy chain to provide a reliable indication of real time and corrected time at remote locations regardless of malfunction of any individual unit.
A still further advantage of the invention is that each unit can be operated as an elapsed timer or as an interval timer without affecting operation of the unit as a master, sub-master or slave clock except for temporary pre-emption of the display.
Other advantages appear hereinafter.